Progress in Pseudotyping Lentiviral Vectors Towards Cell-Specific Gene Delivery In Vivo

Lentiviral vectors (LVs) have become a fundamental tool in gene therapy due to their unique ability to transduce both dividing and non-dividing cells, transfer large genes of up to 10 kb, and facilitate stable, long-term expression of therapeutic genes into target cells. A key application of LVs is the ex vivo genetic modification of patient-derived cells, such as the production of CAR-T cells by transducing isolated T cells with LVs to express the CAR gene, enabling them to target and destroy cancer cells once infused back into the patient. However, these ex vivo gene therapy drugs are often dismally unaffordable due to the complex procedures involved, including cell isolation, genetic modification, and expansion, along with the significant risks associated with immune conditioning to ensure successful engraftment. To overcome these barriers, direct in vivo transgene delivery to physiologically relevant cells has been explored, bypassing the need for ex vivo manipulations and reducing costs. Yet, a major challenge in this approach is engineering LV cell tropism to ensure the precise targeting of specific cells while avoiding off-target effects. Recent advances in modifying LV surface proteins have shown promise, including the successful in vivo generation of CAR T cells and ensuing clinical trials. This review is aimed at providing an up-to-date account of the progress in engineering LV tropism, covering the utility of different heterologous viral envelopes and their engineering to achieve cell-type-specific delivery and host immune evasion, and highlighting the potential of in vivo gene therapy to improve the affordability and accessibility of life-saving treatments.